I saw an episode of American Muscle Car where they put a series of
engines on a dynamometer to determine the real horsepower of 5 legendary
Muscle Car engines.

I am pretty sure one of the engines was smoke dope, or the dyno
operator was. But we will get to that in a minute.

The premise of the show was to determine how much horsepower these
engines really made. In the day the manufacturers lied a lot about
horsepower. There were to main reasons to lie. 1) Insurance rated were
climbing sky high and the insurance industry went by the horsepower
rating to help them price out insurance. A car with 290 hp was going to
be easier to insure than the same car with a 400 hp engine. 2) Racing.
Cars and their engines were put into classes in racing, mostly drag
racing. A car with a factory rating of 335 hp would be put into a lower
class. The fact that the car really had over 400 hp helped it win racing
in this lower class.

So, how much did they lie back then. Well, it is hard to say. I
remember hearing that one trick for lieing was to just use the
horsepower at a different RPM. Let's say you have an engine with a
horsepower rating of 450 hp @ 6200 RPM. YOU take the horsepower rating
at 5000 RPM, a conservative 360 hp. Genius!

AMC showed 5 engines that were rebuilt to exact factory specs. These
were restoration rebuilds, where factory spec or "blueprint" parts were
used. So what engines, and what were their real horsepower.

Engine

Factory Rating

AMC Dyno Results

Chevrolet "Fine" 409

409 hp

406 hp

Ford 427 "Hi-Riser"

425 hp

637 hp

Pontiac 421 Super Duty

405 hp

488 hp

Chrysler 426 Hemi

425 hp

820 hp

Chevrolet L88 427

425 hp

527 hp

Let's take a look at these numbers. She's So Fine, My 4-0-9. I was
not too surprised that 409 came very close to it original horsepower
rating. This engine came out before the insurance problems of the times
and Chevrolet may or may not have been directly involved in racing at
the time.

I was a little surprised about the Ford 427. I don't remember exactly
what they said on the show, but they mentioned something about using a
medium riser manifold because that's what they had available. I would
not have guessed over 600 horsepower, but I supposed it is possible. I
would have guessed 525-550.

Next up the Pontiac SD 421. For those of you that don't remember, Car
and Driver did an article in 1964 comparing a Pontiac GTO to a Ferrari
GTO. The problem with that article was two-fold. First, they didn't
actually have a Ferrari to do the comparison. They used previous test
data on the Italian Goat to compare against the American car. That
wouldn't be bad enough, except the car Pontiac supplied to Car and
Driver had... you guessed it... a SD 421 engine instead of the 348
engine it was supposed to have. So, the SD 421 was also underrated. This
is not surprising as Pontiac ruled the drag strips with the Super Duty
cars.

Let's go out of order for a moment and cover the L-88 Corvette. The
L-88 is quite rare. Vettes with this engine will fetch six figures. In
the day this engine was geared toward stock car drag racing. Chevrolet
didn't want regular people buying it. They wanted racers buying it. So,
they rated it at 425 hp. Racers knew this was bogus. At the time, they
hoped to fool the regular guy that went into a dealer and checked the
option box next to the highest horsepower. The highest horsepower engine
was a 427 with 3 - 2 barrel carbs rated at 435 hp. Racers knew the L-88
was good for over 500 hp. And we hit that well here. This one seems
right on to me.

Finally we come to the legendary Hemi. No. That was not a typo. The
engine they ran generated 820 horsepower, and it did it at 6400 RPM.
Now, I know a little about engines, and I can tell you for a fact... an
engine is not going to make 2 hp per cubic inch at only
6400 RMPs without some kind of force induction. You need air and fuel in
the combustion camber to make power. A normally aspirated engine, even
at 100% volumetric efficiency is not going to make this much power
unless you rev it out to something like 8000-9000 RPM.

What's worse is that why would anyone buy a 526 cubic inch crate Hemi
rated... accurately... at 610 hp when if you could build a stock 426
hemi and get over 800 horsepower. Look at it this way... if the 426 Hemi
really was make over 800 horsepower in the day why weren't Hemi powered
cars racking up significantly faster times in road tests that 454
powered Chevelles or L-88 powered Corvettes.

Either the dyno operator or the engine were smoking dope. The 426
Hemi never made 820 horsepower is stock trim. Period!

Conclusion

Well, except for the bogus numbers on the 426 Hemi this was a very
informative show. However, I would have liked to see a handful of other
engines. Let's see, here are 5 more engines I would have liked to see
put on a dyno for an accurate reading:

Chevrolet 302 Z-28 - This engine was rated at 290
hp. People think it was actually closer to 400 hp. It certainly could
rev, and I would love to know what it really was capable of.

Ford Boss 302 - This would be the ultimate dyno
shootout, the 302 Z/28 engine versus the Boss 302. Of course Ford rated
this engine at... yep, 290 hp. With intake valves in those Cleveland
cylinder heads the same size as a big block Chevy, this engine shoud be
able to out breath the Chevy small block. But could the engine hold
itself together long enough to generate a high rating. Hmmm.

Chevrolet LS-6 454 - This engine was rated at 450
hp, the highest horsepower rating of any Muscle Car engine from the era.
How much power did it really make? I owuld like to know.

Buick 455 Stage I - This is the torque champ. Rated
at 510 ft/lbs of torque it was rated the highest rated torque rating of
any engine at the time. But it was only rated at 360 horsepower. Stage I
Buicks ran right there with Hemi and LS-6 powered cars. How much power
did it really have?

Chrysler 426 Hemi - Yea, they already did it. But
they botched it up so badly that I want to know what a real
426 Hemi would put out.